Any cleaning as others have said devalue a silver coin, or any coin for that matter. There are many grades that the coin dealers use to grade collectable coins. Long ago I learned that what ever I pulled out of the ground and handled with loving care graded so far down the list that the time spent wasn't worth the effort. Now I just glance at the date and drop it in a jar.
HOWEVER, it is important to know the KEY DATES so you don't spend a good coin.
Just my two cents,
Sandman